A simple apparatus for vertical flat-sheet polyacrylamide gel electrophoresis

Cleavage map of the simian-virus-40 genome by the restriction endonuclease III of Haemopholus aegyptius

Enzymic digestion of Simian virus 40 (SV40) DNA with Haemophilus aegyptius restriction endonuclease Hae III results in 10 major and eight minor fragments. These were resolved by electrophoresis on graduated polyacrylamide slab gels. All fragments have been characterized with respect to the size relative to the Haemophilus influenzae Rd fragments (Hind). They were ordered on the SV40 DNA map by means of overlap analysis of the double cleavage products derived from sequential digestion of Hind fragments with Hae III endonuclease and Hae fragments with Hind II + III enzyme, as well as by other reciprocal cleavage experiments, including those involving Haemophilus para-influenzae fragments. In this way the 18 Hae III cleavage sites and the 13 Hind sites have been localized on the circular SV40 DNA map.

Chromoplasts of Tropaeolum majus L.: Isolation and characterization of lipoprotein elements

Chromoplasts of unfolding petals of Tropaeolum majus contain large amounts of filaments (which, in sections, appear as tubules), and unevenshaped, isodiametric to elongated bodies (IBs). These structural elements are the major sites of the chromoplast pigments. They were freed from isolated chromoplasts and subjected to sucrose density gradient centrifugation. At a density of 1.080 g cm(-3) a distinct orange band contained almost exclusively fine filaments of 15-20 nm in diameter as shown after negative staining. Other filaments and most of the IBs were heterogeneous in size, shape, and density and were collected in two fractions of buoyant densities of 1.025 and 1.055 g cm(-3). The three fractions thus obtained comprise 15-33% protein, large amounts of carotenoids and their esters, glyco- and phospholipids, as well as minor amounts of tocopherols. A higher buoyant density of particles is correlated with a higher relative content of protein and glyco- and phospholipids and a lower relative content of carotenoids. The polypeptide pattern, as shown by SDS-polyacrylamide gel electrophoresis, is very similar in all three fractions. There is one main polypeptide, with a MW of about 30,000, accounting for up to 80% of the protein of each fraction.

Biosynthesis of lipovitellin by the crustacean ovary. II. Characterization of and in vitro incorporation of amino acids into the purified subunits

The amino acid composition has been determined for two of the five subunits of the crayfish lipovitellin. In addition the molecular weight of each subunit has also been ascertained. Most importantly, it is demonstrated that following in vitro incubation radioactive amino acids are incorporated into each of three purified subunits. These data strongly support the suggestion that the vitellogenic ovary of the crayfish is capable of in situ synthesis of lipovitellin.

Characterization of two cell-envelope fractions from chemotrophically grown Rhodospirillum rubrum

Two cell-envelope fractions were isolated from chemotrophically grown cells of Rhodospirillum rubrum. On the basis of electron-microscopic investigations, chemical analysis, distribution of components involved in respiration, and poly-acrylamide gel electrophoresis, the heavy fraction (rho20 = 1.246 g per cm3) was identified as cell-wall, and the light fraction (rho = 1.145 g per cm3) as cyto-plasmic-membrane fragments. Electron micrographs showed cell-wall fragments as open structures while cytoplasmic-membrane preparations were composed of closed membrane vesicles. With respect to the main classes of chemical compounds, cell wall could be distinguished from cytoplasmic membranes by a rather low ratio of phospholipids per protein and a high ratio of carbohydrates per protein. The relative proportion of individual neutral sugars as well as phospholipids (except for lysophosphatidyl ethanolamine) revealed no significant differences between both envelope fractions. Fatty acid analysis demonstrated a higher proportion of saturated fatty acids in cell-wall than in cyto-plasmic-membrane fractions. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the fractions. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the fractions showed distinct protein compositions. While in cell-wall preparations polypeptides of 43,000 and 14,000 daltons predominated, 56,000- and 52,000-dalton polypeptides were the main protein subunits of cytoplasmic membranes. Cross contaminations of both cell-envelope fractions were defined.

Detection of isoelectric focused antibody by autoradiography and hemolysis of antigen-coated erythrocytes. A comparison of methods

Mouse anti-group A streptococcal carbohydrate (GAC) antibodies were detected in analytical isoelectric focusing (IEF) acrylamide gels by the hemolysis of GAC-coated sheep erythrocytes immobilized in agarose. This procedure is rapid and reproducible but, because it requires diffusion of antibody from the acrylamide gel into the agarose layer, results in poorer resolution than other methods of detection where antibodies can be fixed in the acrylamide gel after focusing, such as protein staining of purified antibodies or autoradiography of 125I-GAC bound to focused antibodies.

New chromosomal location for structural genes of ribosomal proteins

An Escherichia coli mutant, ts9, previously reported by Flaks et al. (Cold Spring Harbor Symp. Quant. Biol. 31, 623-631, 1966) to have an electrophoretically altered ribosomal protein, has been further characterized and the altered component has been identified as L7/L12. Although mutant ts9 is temperature sensitive for growth (rts-), the rts and L7/L12 mutations are genetically separable and are both located between argH and rif. The L7/L12 mutation (rpyL) maps very close to relC, mutants of which have a defect in the 50S ribosomal subunit. The gene order is argH-rts-(rpyL,relC)-rif. Protein synthesis directed by bacteriophage lambdacI857S7drifd18 in ultraviolet-irradiated cells indicates that L7/L12, As well as L1, L10, L11, and possibly L8 or L9 are coded by the phage DNA. Our results indicate that rpyL is the structural gene for L7/L12 and that this region of the E. coli chromosome contains a cluster of structural genes for ribosomal proteins.

Membrane biosynthesis in the frog retina: opsin transport in the photoreceptor cell

Rhodopsin biosynthesis and transport in the photoreceptor cell have been analyzed by subcellular fractionation of frog retinas after short periods of radioactive amino acid incorporation in vivo. Labelled membrane proteins were identified by autoradiography or sodium dodecyl sulfate-polyacrylamide gels. One of the most intensly labeled proteins in retina had a molecular weight comparable to opsin isolated from purified rod outer segments (ROS). Incorporation of label into this protein was rapid; the relative specific activity then diminished after the first 2 hr as radioactivity was transferred from retinal subcellular fractions to ROS. The kinetics of this transfer resembled rates previously observed by Hall et al. (Hall, M. O., Bok, D., and Bacharach, A.C.E. (1969), J. Mol. Biol. 45, 397). To identify the rapidly labeled protein as opsin we devised a new technique of two-dimensional immunoelectrophoresis of detergent solubilized membrane proteins. Antibodies were prepared against both whole ROS and opsin. After initial separation of retinal proteins on sodium dodecyl sulfate-polyacrylamide gels, a second dimension of electrophoresis in agarose, containing antisera, resulted in the formation of specific immunoprecipitates. Immunochemical analysis of all membranous and soluble retinal subcellular fractions indicated that newly synthesized opsin was membrane bound upon completion of synthesis. At no period of incorporation was a soluble form of newly synthesized opsin detectable. On this basis, we suggest that this protein is apparently transported as a water-insoluble membrane-bound molecule through the cytoplasm or along membranes of the inner segment to its assembly site near the base of the outer segment.

Physical properties of some ribosomal proteins in solution and evidence for molecular interactions between isolated ribosomal proteins

Many previous studies have been directed toward obtaining a physical visualization of the relationship between the protein and RNA in the ribosomal subunits isolated from Escherichia coli. The current study is the first report where an attempt has been made to directly assess interactions between a pair of isolated ribosomal proteins separate from the intact system by means of sedimentation equilibrium analysis. The molecular weights of the proteins S3, S4, S5, S6, S7, S8, and S20 from the 30S subunit of the E. coli ribosome were determined under conditions of assembly of the subunit by sedimentation equilibrium. All of the proteins exhibited molecular weights consistent with monomeric behavior (i.e., in agreement with the measurement of the ultimate molecular weight in denaturing solvents as reported in other studies as well as in the current study) except S8 which indicates a tendency to self-associate. Hydrodynamic measurements on the proteins indicate that these proteins are not completely disorganized in solution such as a random coil, although not as compact as globular proteins. The frictional coefficient ratios found for these ribosomal proteins range from 1.4 to 1.9. The hydrodynamic data are discussed as containing some evidence that stable interaction sites could exist in the proteins. The molecular weight data are considered pertinent to a sedimentation equilibrium study of protein-protein interactions that may be occurring in the ribosomal subunits. Two proteins, S3 and S5, considered in this investigation were found to exhibit no tendency to self-associate under conditions of reassembly. When the two proteins are mixed under those same conditions, however, a species with a molecular weight greater than that of either S3 or S5 is observed to be formed. The interpretation is presented that a molecular interaction between S3 and S5 is the cause. The system is described as containing S3, S5, and a complex between S3 and S5 with a stoichiometry of 1:1 and an association equilibrium constant of 5.7 times 10-5 l./mol (delta G-o equals minus 7.25 kcal/mol). Since the association appears to be specific and of moderate strength, it is concluded that the interaction could have some pertinence with respect to conferring a structural arrangement in the ribosomal subunit. Moreover, it is concluded that protein-protein interactions, in general, must be considered in addition to the well documented significant RNA-protein relationships when models for ribosome structure and assembly are formulated.

Individual histone messenger RNAs: identification by template activity

Newly synthesized polysomal messenger RNAs from cleavage stage embryos of the sea urchin Arbacia punctulata and Lytechinus pictus that contain putative histone mRNAs have been fractionated on 6% polyacrylamide slab gels. At least 8 RNA species with unique electrophoretic mobilities have been recognized. The complex of RNAs has been eluted from the gels in three groups, A, B, and C, in increasing order of mobility. The template activity of the three fractions and the unfractionated starting material was examined in the mouse Krebs II ascites tumor cell-free protein synthesizing system. The unfractionated messenger complex programs the synthesis of proteins that co-electrophorese exclusively with sea urchin histones in both sodium dodecyl sulfate and acid urea gel systems. The products of in vitro protein systhesis stimulated by the individual polyacrylamide gel RNA fractions were similarly examined. Each stimulated protein synthesis and was enriched for specific histone templates. We conclude that RNA fraction A is template for histone f1, C is template for histone f2a1, and B serves as template for f2b, f2a2, and f3 histones. A minor degree of contamination of the A and B RNA fractions was obvious from the production of other histones by each template. The co-electrophoresis of specific template activity with specific radiolabeled RNAs supports the concept that most or all of the labeled RNAs are indeed themselves the histone mRNAs.

Identification of a ribosomal protein essential for peptidyl transferase activity

Extraction with 2 M lithium chloride removes a group of proteins (LiC1 SP) from 50S ribosomal subunits. Both the LiC1 SP and the resulting cores, which contain the remaining proteins as well as 5S and 23S RNA, lack peptidyl transferase activity, as measured by the "fragment reaction". Activity can be restored to the LiC1 cores by reconstitution with LiC1 SP under conditions of high temperature and high ionic strength. The LiC1 SP proteins were fractionated by carboxymethyl-cellulose and Sephadex G-100, and the individual fractions were tested by this reconstitution system. Of the 18 ribosomal proteins found in the LiC1 SP, only L16 is essential for reconstitution of peptidyl transferase activity.

Purification and kinetic properties of chalcone-flavanone isomerase from soya bean

The chalcone-flavanone isomerase from soya bean seed has been purified 8300-fold. A molecular weight of 15,600 plus or minus 1000 has been determined for the enzyme. Effects of iodoacetamide and sodium tetrathionate on the enzyme, and pH dependence of the catalytic step, indicate that a sulphydryl group is not involved in the reaction mechanism and the catalytic group is probably an imidazole side chain in the basic form. The kinetics of the isomerisation of isoliquiritigenin to liquiritigenin have been examined and show that at pH 7.6 the reaction is reversible with an equilibrium constant of 37 in favour of flavanone. A number of flavonoid compounds competitively inhibit the reaction, suggesting a possible regulatory role for this enzyme in flavonoid biosynthesis.

The partial characterization of purified nitrite reductase and hydroxylamine oxidase from Nitrosomonas europaea

Nitrite reductase has been separated from cell-free extracts of Nitrosomonas and partially purified from hydroxylamine oxidase by polyacrylamide-gel electrophoresis. In its oxidized state the enzyme, which did not contain haem, had an extinction maximum at 590nm, which was abolished on reduction. Sodium diethyldithiocarbamate was a potent inhibitor of nitrite reductase. Enzyme activity was stimulated 2.5-fold when remixed with hydroxylamine oxidase, but was unaffected by mammalian cytochrome c. The enzyme also exhibited a low hydroxylamine-dependent nitrite reductase activity. The results suggest that this enzyme is similar to the copper-containing ;denitrifying enzyme' of Pseudomonas denitrificans. A dithionite-reduced, 465nm-absorbing haemoprotein was associated with homogeneous preparations of hydroxylamine oxidase. The band at 465nm maximum was not reduced during the oxidation of hydroxylamine although the extinction was abolished on addition of hydroxylamine, NO(2) (-) or CO. These last-named compounds when added to the oxidized enzyme precluded the appearance of the 465nm-absorption band on addition of dithionite. Several properties of 465nm-absorbing haemoprotein are described.

Electrophoretic separation of different phophosproteins associated with Ca-ATPase and Na, K-ATPase in human red cell ghosts

Ca has been found to increase the quantity of (32)P incorporated into red cell ghosts from [gamma-(32)P]ATP over the levels obtained by incubation with Mg alone or with Mg + Na, in correlation with the effect of Ca on the associated ATPase activities. When the (32)P-labeled ghosts were solubilized in sodium dodecyl sulfate (SDS) and electrophoresed on acrylamide gels only two bands could be detected either by autoradiography or by counting the sliced gels. The faster moving band (P-2) had the same mobility and the same molecular weight (103,000) as the phosphoprotein found either with Mg alone or with Mg + Na. The slower moving band (P-1) was not found in extensively washed ghosts labeled in the absence of Ca. The molecular weight of P-1 is approximately 150,000. P-1 like P-2 was not affected by pretreatment of intact cells with Pronase before labeling indicating that neither the phosphorylating mechanism nor the phosphoprotein are accessible to externally applied Pronase. The demonstration that a Ca-phosphoprotein is separable from the Na-stimulated phosphoprotein suggests that the Ca-ATPase is distinct from and independent of the Na,K-ATPase. The fact that Ca blocks the dephosphorylation by K of the Na-phosphoprotein indicates that caution is required in interpreting results when the activities of the different phosphoproteins have not been separately determined.